I'd like to go back to my question about whether or not people could buy or sell this thing.

Let's call Basic Income Share (BIS) one entry in the database.  It's basically the name of one person, some bitcoin address or something, along with some proof that this person does exist and a way to identify him (with biometrics).

Let's give a different name to the amount one person actually receives each month.  Let's call it BIR (Basic Income Right).

Ok so one person "owns" a BIS and that allows him to receive one BIR each month.

Question:  do I have the right to sell my BIS?

I mean, can we allow people to give an order such as:  "I'm the owner of BIS n°XXXXX.  Here is cryptographic proof of this assertion.  From now on, all my BIR will go to the owner of BIS n°YYYYY"  ?

I don't see why it should not be allowed.  If people have the right to own things, they should have the right to give them away (and in particular, to sell them).   Plus, if you forbid this, a black market will probably emerge.

So assuming I do have the right to sell my BIS, I also have the right to buy some.  In effect, it is just as if the State was turned into an anonymous society (not sure of the english term.  Corporation maybe).

Some people would have a lot of BIS, some people would have very few.   So we'll be very far away from your initial project.

Your system would look like capitalism, but it would be much worse.  Because this "big state" would be a giant company whose income does not come from free trade, but taxation.   This should be a nightmare to everyone.